Air permeable cladding panel

ABSTRACT

The present invention relates to a cladding material, for a building or other construction. The cladding material comprises an outer air permeable cover ( 3 ) an inner air permeable cover ( 4 ) and an intermediate layer ( 2 ). The intermediate layer has a graduated filtering profile for allowing selective particle filtration, thereby enhancing filtration through depth and hence delay clogging.

The present invention relates to cladding and in particular, but notexclusively, to such cladding when applied to buildings located inrelatively polluted areas.

In this regard, airborne particulate and gaseous pollution is known tohave a hugely detrimental effect on human health. In conventionalbuildings, much emphasis is placed on achieving airtightness and lowinfiltration losses, with controlled fresh air intake ducted into thebuilding using a mechanical Heating, Ventilation and Air Conditioning(HVAC) system. Floor and wall apertures are traditionally specified inCodes of Practice to provide trickle ventilation, with opening sizespecified on the basis of floor area. Thermal insulation in suchbuildings passively curtails conduction heat loss, to achieve energyefficiency. This outlines the tried-and-tested approach, and though itcontinues to be technically valid, its drawbacks are high capital andmaintenance costs and tight minimum ventilation quotas to limit heatingenergy demand. In some cases, illnesses known as ‘Sick BuildingSyndrome’ have been attributed to inherent design shortcomings, poorimplementation or lax maintenance of the HVAC installation itself.

The current UK Government has declared its commitment to reduce theconcentration of airborne particulate matter (Review of Air QualityStrategy, 2001). Significant research has been carried out in recentyears to understand the effect of particulate matter on human health(Seaton et al, 1995; COMEAP, 1998). Nonetheless, uncertainty stillexists. The potential effects are substantial enough, however, for theUK Government to recommend that the precautionary approach be applied tothe issue of particulate emissions. This asserts that the potential riskshould be reduced to as low as is reasonably practicable even thoughthere is much that is still not understood.

Efforts to derive a strategy to minimise particulate emissions have beenproblematical. Much of the problem is due to the source and location ofsource of particulate matter.

In this regard, the source of particulate air pollution in cities isprincipally derived from;

-   1. Primary particles—from the products of incomplete combustion    (mainly road traffic, electricity production, building space    heating)-   2. Secondary particles—formed in the atmosphere from the chemical    reaction of sulphurous and nitrous emissions.-   3. Biological particles—re-suspended road dust, construction,    quarrying, sea salt, agricultural.

Each source is responsible for roughly a third of the total of urbanbackground concentration. In the UK, typically 80% of emissionsoriginate from UK sources but this percentage can fall if certain windconditions exist. Anti-cyclone wind conditions can cause this figure tofall to 50% (or lower in the SE of England). Current strategies to limitparticulate emissions concentrate on front of pipe solutions, mitigatingor eliminating emissions from diesel engines and power plants forinstance.

However, due to the diverse nature and location of the sources ofparticulate matter, the original limits set in initial World HealthOrganisation guidelines in 1997 were rejected as unattainable. Theseinitial World Health Organisation guidelines could not have been met,for instance, even if the utopian situation of no road traffic were tobe achieved. The limits were thus increased.

It is clear, therefore, that an alternative strategy is required to dealwith removal of particulate matter from the atmosphere.

In this respect some work has been undertaken by the inventors of thepresent application in providing a “breathable” wall cladding forbuildings, whereby the building is provided with panels which arepermeable to air and which include a single insulating layer. Air flowsthrough the panels, driven by a negative differential in pressurebetween the interior and exterior of the building. Air that flows intothe building picks up heat that is being conducted outwards, thusfurther improving the building's space heating performance. Theinsulation media provides filtration characteristics such thatparticulates can be trapped by the insulation as they pass through thecladding. However, the inventors have identified problems in relation toclogging of the insulation which reduce the effectiveness of the“breathable” wall cladding concept.

An object of the present invention is to alleviate the problemsidentified above.

According to a first aspect of the present invention there is provided acladding material comprising:—an outer air permeable cover; an inner airpermeable cover; and an intermediate layer, wherein the intermediatelayer is provided with a graduated filtering profile.

With respect to the intermediate layer, the development of a graduatedfiltering profile has been found to enable selective particlefiltration, to enhance filtration through depth within the intermediatelayer and hence delay clogging. This thereby avoids the existence ofpredominantly surface filtration and rapid filter-cake deposition thatcan lead to premature clogging.

Preferably, the filtering characteristics of the intermediate layer aresuch as to trap relatively large particles (>10 μm) towards the outercover end of the intermediate layer and to trap relatively smallerparticles (0.01 μm) towards the inner cover end of the intermediatelayer. With constant filter loading, (i.e. static particulate pollutionlevels) and a uniform rate of particle deposition through depth, thelife of the intermediate layer would then be a function of the layer'sthickness. All things being equal, as layer thickness is increased thenso does the volume (per unit area of cladding) available for particlecapture and sequestration increase.

Of comparable significance, the graduated filtering profile also permitsincorporating materials that have been optimised for the filtration ofgaseous pollutants and biological agents' (or contaminants). Adsorptionof gases generally requires large surface area of the media and longresidence time of the incoming gas in contact with this media to workeffectively. Both conditions are satisfied with dynamic insulation usedover a large wall area. For example, any natural fibre presented n thecorrect packing density and thickness could be used to filter a reactivespecies such as ozone, as well as capturing ultra-fine particulates.

Alternative solutions to clogging, such as incorporating “mufti-stage”disposable filter layers in the design, are also possible. A cloggedlayer could simply be ‘peeled-off’, and safely disposed of to expose afresh filter surface every few years. It is thus realistic to target alife in excess of 20 years before entire wall panels have to bereplaced, or possibly regenerated, irrespective of the clogging riskoutlined. It is worth noting at this point that the problem of prematureclogging becomes less significant the more buildings per city block aredynamically insulated, an important factor to consider when specifyingthis construction form in a heavily polluted urban setting.

In preferred embodiments, the cladding material has other featuresincluding thermal and/or sound insulating properties for energyefficiency and indoor ambiance.

Conveniently, the intermediate layer comprises one or more of:—mineralwool, wet-blown cellulose, glass wool or any other suitable fibrematerial.

Preferably, the intermediate layer is provided in the form of one ormore of:—membranes, fibers, pulp or cellular based (foam or sponge)materials, modified aerated concrete, or other such materials which arecost effective and readily available. The intermediate layer maycomprise additional components to provide structural support, tofacilitate uniform airflow through the insulation media, to provide airdistribution, prefiltration, heating, cooling and/or dehumidificationand may provide sealing components to stop undesirable air leakage atborders and edges.

The cladding material may be provided in the form of a StructuralInsulation Panel (SIP) and may comprise materials possessing filtrationproperties specific for one or more of:—particulate emissions, gaspollutants, chemical agents and biological agents.

In preferred embodiments, the cladding material is provided in the formof panel units. Conveniently, the panel units are provided in modularformat. Implemented in a modular format, walls can be fabricated fromsuch panel units comprising layers of different materials withcomplementary particulate filtration characteristics, one or more ofwhich could additionally enable filtration of gaseous pollutants,chemical and/or biological agents, etc. The adoption of a modularapproach is important, since the panels can ultimately be produced in avariety of shapes, sizes and finishes to meet the demands of a diverseconstruction market, optimised for either new-build or retrofitting, andmass produced to keep costs low and availability high.

Preferably, the intermediate layer may be formed of a plurality ofseparate air permeable filter layers, of different, yet complementaryfiltering characteristics. The intermediate layer may alternatively beformed of a single filter layer, whose filtering characteristics varyacross its thickness. The or each filter layer of the intermediate layermay be independently replaceable, whereby a clogged filter layer can beremoved and replaced or reconditioned when required.

In preferred embodiments, the or each filter layer of the intermediatelayer may comprise one or more disposable filter elements. If clogged,such filter elements can be removed, for example as discussed above, by“peeling off” and safely disposed of to expose a fresh filter surface.The lifespan of the panel can be prolonged in this manner.

In preferred embodiments where a plurality of filter layers are present,each filter layer of the intermediate layer is selected to extract aspecified range of particle sizes, gaseous pollutants, and/or biologicalagents. Conveniently, the separate filter layers of the intermediatelayer together define substantially the complete filtration spectrum ofparticulate and other pollution.

In preferred embodiments, the cladding material is for a building orother construction. Other embodiments without limitation include air,land and sea vehicles, tunnels, roads, car parks, and various otherconstructions.

The cladding material may be combined with other components, such asglazing, renewable energy devices, or smart elements as part of acomposite modular panel unit.

According to a second aspect of the present invention there is provideda cladding system for cladding a building or other constriction at aparticular location, comprising the steps of:—

-   a) identifying the nature of pollutants at that location;-   b) establishing an appropriate filter configuration for that    building or other construction at that location;-   c) forming cladding panel units for the building or other    construction, the panel units having a graduated filtering profile    across their thickness according to the filter configuration; and-   d) applying the panel units to the building or other construction.

The present invention further encompasses a building or otherconstruction comprising a plurality of panels formed of claddingmaterial as defined above and a building or other construction claddinglayer for use in cladding material as defined above, the cladding layerhaving a graduated filter profile.

According to a third aspect of the present invention there is provided abuilding or other construction cladding panel comprising anair-permeable material, the material further being configured to filterout harmful chemical and/or biological agents.

According to a fourth aspect of the present invention there is provideda system for improving air quality in a particular location, the systemcomprising the steps of:—

-   a) placing at that location a building or other construction    adopting air permeable cladding material; the cladding material    comprising a filtration layer for removing one or more    of:—particulate emissions, gas pollutants, chemical agents and    biological agents as air passes from the exterior of the building or    other construction to its interior; and-   b) arranging for filtered air from within the building or other    construction to pass to the exterior of the building or other    construction.

The present invention hence provides for a pollution removingdynamically insulated, air permeable cladding material, that also canenhance energy efficiency for internal heating and/or cooling. Whenapplied to a building or other construction, fresh ventilation air canbe pre-heated (or cooled) and filtered as it is drawn into the buildingor other construction through a durable, purpose-designed porousbuilding envelope. A new type of ‘breathing wall’ cladding panel ishereby provided enabling urban environments to be developed that areless polluted and healthier to live in, and contributing positively tosustainable future development.

Dynamic insulation permits the movement of air through an air permeable,dynamically insulated wall. This reduces conduction heat loss (or gainin cooling applications) and provides a method of bringing filteredfresh air into the building. The materials needed to achieve this (i.e.,possessing appropriate insulation and permeability characteristics) areavailable, and include conventional insulation materials such as mineralwool, wet-blown cellulose and glass wool. A well designed dynamicallyinsulated building or other construction can dispense with large heatingand ventilation plant and ancillaries (ducting, etc.), allow highercontrolled ventilation rates to be achieved, and reduce fossil fuelconsumption by cutting out conduction heat fluxes. They effectivelyenable any desired building fabric heat-loss-coefficient, or U-value, tobe achieved using thinner than conventional walls in a range of buildingand other construction types, including multi-storey buildings, easilysurpassing current UK and European Building Standards and Regulations.

An embodiment of the present invention will now be described by way ofexample with reference to the drawing in which:—

FIG. 1 shows schematically a cross-section taken through a section ofcladding according to the invention.

As shown in the example of, FIG. 1, the invention concerns a multi-layercladding panel 1 of modular construction, comprising a seriesarrangement of one or more air permeable intermediate or internal layers2 of varying properties and thickness contained within an, optionalvented outdoor-facing weatherproof cover 3 and an optional indoor-facingwearing surface cover 4.

The panel may contiguously incorporate the above components.Alternatively, the internal layers may be bonded directly to discreteouter and inner covers, or separated by one or more air plenums, withadditional (not shown) structural support, air distribution,pre-filtration, heating, cooling and/or dehumidification and sealingcomponents, depending on design/fabrication requirements. In operation,fresh ventilation air is drawn into the building or other constructionthrough such cladding panels forming all or part of the envelope (skin)of the building or other construction, and stale air is exhausted fromthe building or other construction, through an outlet duct to atmosphere(not shown). Used over a sufficiently large area of the buildingenvelope, the panels will provide heat and sound insulationcharacteristics that surpass existing regulations and standards. Moreimportantly, as air is slowly drawn into the building or otherconstruction through the panels, the different internal layers will eachextract a fraction of the overall particulate content and other forms ofpollution from the air flow in a manner commensurate with theirindividual filtration characteristics. Such characteristics may includeporosity, permeability, packing density, fibre size (in the case offibrous insulation), as well as chemical properties, biologicalproperties, etc.

This gradation of complementary filtration properties of theintermediate or internal layer 2 may be provided by using separatefiltration layers as shown, or by use of a single contiguous layer ofair permeable insulation. The cumulative effect of this combination ofinsulation layers or gradation of properties is permanent removal ansafe sequestration of substantially all pollution from the air beingused to ventilate the building or other construction, and in timecleaning of the outdoor environment itself.

The multi-layer construction or graduated single layer construction andthe selection of the filter characteristics of the layers facilitatesfiltration through the depth of the cladding panel, which correctlyimplemented prevents pre-mature clogging of the panel and ensures anacceptable service life before replacement or refurbishment is required.This provides a unique and innovative solution to the air pollutionproblem, including the unchecked hazards of particulates. Buildings orother constructions using such cladding panels, in the manner described,will act to preserve the health and well-being of both building occupantand the surrounding outdoor environment as part of their normaloperation, unlike the conventional buildings of today which do neither.

To function correctly in a specific building or other construction, thecladding material requires appropriate filtration and pressure dropproperties across its component layers, good thermal and soundinsulation, and resistance to environmentally induced degradation to beestablished.

The intermediate layers 2 may be formed of membranes, fibres, pulp, orcellular-based (foam or sponge) materials, or modified aerated concrete.The range of applications across the filtration spectrum spans the ionic(atomic radius) to the macro-particle (fine sand) ranges. Fibres presentan attractive choice for use in dynamically insulated buildings due totheir efficacy in the PM_(2.6)-PM₁₀ range at the flow velocities ofinterest, wide availability, utility, low cost, and prevalence asconventional building insulation materials.

The cladding may further comprise materials for gaseous adsorption orroom-temperature catalytic conversion of for example COx, NOx, Sox andozone, Chemical and biological agent filters can also be included aspart of an enhanced cladding panel design.

The or each filtration layer of the intermediate or internal layer 2 maycomprise one or more disposable filter elements. If clogged, such filterelements can be removed, for example by “peeling off”, and safelydisposed of to expose a fresh filter surface. The lifespan of the panelcan be prolonged in this manner.

Where a plurality of filter layers are present, each filter layer of theintermediate layer can be selected to extract a specified range ofparticle sizes.

The present invention is not to be limited in scope by the specificembodiment described herein. Indeed, various modifications of theinvention will become apparent to those skilled in the art from theforegoing description and accompanying figure. Such modifications areintended to fall within the scope of the appended claims.

1. A cladding material comprising:— an outer air permeable cover; aninner air permeable cover; and an intermediate layer, wherein theintermediate layer is provided with a graduated filtering profile.
 2. Acladding material according to claim 1, wherein the filteringcharacteristics of the intermediate layer are such as to trap relativelylarge particles towards the outer cover end of the intermediate layerand to trap relatively smaller particles towards the inner cover end ofthe intermediate layer.
 3. A cladding material according to claim 1wherein the intermediate layer has thermal and/or sound insulatingproperties.
 4. A cladding material according to claim 1, wherein theintermediate layer comprises one or more of:—mineral wool, wet-blowncellulose and glass wool.
 5. A cladding material according to claim 1,wherein the intermediate layer is provided in the form of one or moreof:—membranes, fibres, pulp or cellular based (foam or sponge)materials, or modified aerated concrete.
 6. A cladding materialaccording to claim 5, wherein the intermediate layer comprises fibres.7. A cladding material according to claim 1, wherein the claddingmaterial comprises filter materials for one or more of:—particulateemissions, gas pollutants, chemical agents and biological agents.
 8. Acladding material according to claim 1, wherein the cladding material isprovided in the form of panel units.
 9. A cladding material according toclaim 8, wherein the panel units are provided in modular format.
 10. Acladding material according to claim 1, wherein the intermediate layeris formed of a plurality of one or more separate filter layers, ofdifferent filtering characteristics.
 11. A cladding material accordingto claim 10, wherein each filter layer of the intermediate layer isselected to extract a specified range of particle sizes, gaseouspollutants, chemical pollutants, and/or biological agents.
 12. Acladding material according to claim 11, wherein the separate filterlayers of the intermediate layer together define substantially thecomplete filter spectrum of particulate and other pollution.
 13. Acladding material according to claim 1, wherein the intermediate layeris formed of a single filter layer, whose filtering characteristics varyacross its thickness.
 14. A cladding material according to claim 13,wherein the or each filter layer of the intermediate layer isindependently replaceable.
 15. A cladding material according to claim13, wherein the or each filter layer of the intermediate layer comprisesone or more disposable filter elements.
 16. A cladding system forcladding a building or other construction at a particular location,comprising the steps of:— a) identifying the nature of pollutants atthat location; b) establishing an appropriate filter configuration forthat building or other construction at that location; c) formingcladding panel units for the building or other construction, the panelunits having a graduated filtering profile across their thicknessaccording to the filter configuration; and d) applying the panel unitsto the building or other construction.
 17. A building or otherconstruction comprising a plurality of panels formed of claddingmaterial according to claim
 1. 18. A building or other constructioncladding layer for use in the cladding material according to claim 1comprising a graduated filter profile.
 19. A building cladding panelcomprising:— an air-permeable material, the material further beingconfigured to filter out harmful chemical and/or biological agents. 20.A system for improving air quality in a particular location, the systemcomprising the steps of:— a) placing at that location a building orother construction adopting air permeable cladding material; thecladding material comprising a filtration layer for removing one or moreof:—particulate emissions, gas pollutants, chemical agents andbiological agents as air passes from the exterior of the building orother construction to its interior; and b) arranging for filtered airfrom within the building or other construction to pass to the exteriorof the building or other construction.
 21. A system for improving airquality according to claim 20, comprising a cladding material including:an outer air permeable cover; an inner air permeable cover: and anintermediate layer, wherein the intermediate layer is provided with agraduated filtering profile.
 22. A durable cladding materialcomprising:— an outer air permeable weatherproof cover; an inner airpermeable wearing surface cover; and an intermediate layer, wherein theintermediate layer is provided with a graduated filtering profile forthe removal of one or more particulate, gaseous, chemical and biologicalpollutants and contaminants.
 23. (Cancelled)
 24. (Cancelled) 25.(Cancelled)